Quantum Leap is an American science fiction television series, created by Donald P. Bellisario, that aired on NBC for five seasons, from March 26, 1989, to May 5, 1993. The series stars Scott Bakula as Dr. Sam Beckett, a physicist who, believing he has invented a way to travel through time, voluntarily subjects himself to an experiment that he believes will prove the validity of his controversial theories. Sam “leaps” into the fluid of spacetime and apparently disappears forever. However, it is soon revealed that Beckett's consciousness is alive and able to transfer to and inhabit the bodies of other people existing on his timeline. The artificially intelligent computer he created operates with the assumption that in order to return home, Sam must change events in the past in order to "correct" the future course of events, which have somehow been changed in an undesirable way by an unknown agent.

Dean Stockwell co-stars as Rear Admiral Al Calavicci, Sam's womanizing, cigar-smoking companion and best friend, who appears only as a hologram. Al is able to research the life Sam currently inhabits, providing advice when needed, and he is the only person able to see Sam when Sam has travelled through time, and is therefore the only witness who can testify that project Quantum Leap has been successful.

The series, which combines humor, drama, romance, social commentary, and science fiction, was ranked number 19 on TV Guide's "Top Cult Shows Ever" in 2007.

A revival series, following the original show's continuity, premiered on NBC on September 19, 2022.